On a bright afternoon in San Diego, three-year-old Aisha was playing outside as her father sat close by, somewhat distracted. Aisha, eager for her father’s attention, waved a toy in his direction. When he didn’t react, she intensified her efforts by tapping him lightly on the head with the toy. She gazed at his face, hoping for a response, but none came. Undeterred, Aisha proceeded to wave the toy even more vigorously in front of her father’s face, brushing it over his head until he finally relented and turned his attention to her as she played on the swings.

Like many toddlers, Aisha can be quite a bundle of energy. However, Aisha is not your typical three-year-old; she’s an orangutan, now aged 11, residing with her family at the San Diego Zoo. Her days as a youngster involved a mix of play, eating, sleeping, and regularly seeking her parents’ attention. Aisha’s interactions with her father are reminiscent of scenes you might observe between a restless child and a distracted parent in a grocery store line. This raises a question: Where does this compulsion to pester or tease come from? Are the similarities in behavior between Aisha and a human child just coincidental, or do they reveal fundamental similarities in how we play, learn, and think?

For the past few years, my colleagues and I have been exploring the nature of teasing among humans and great apes, trying to understand its origins and evolutionary purposes. Teasing sits ambiguously between playful interaction and aggression. It can lead to negative outcomes like bullying, yet it can also be affectionate and charming. In humans, playful teasing, which includes activities like clowning around, playing pranks, and making jokes, is a critical social tool. It allows individuals to experiment with and learn about social boundaries, testing what behaviors are acceptable and what are not, while also showcasing the strength and resilience of personal relationships (picture friends jokingly insulting each other). We believe similar dynamics are at play among other great apes. Although humor has traditionally been seen as a uniquely human feature, our research suggests its roots are surprisingly deep.

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My interest in the origins of humor began in 2005 during my Ph.D. research on orangutan communication. At a zoo, I observed a young orangutan play a teasing game with her mother, offering her a piece of bark and then pulling it away as her mother reached for it. This interaction, which continued several times with roles reversing, struck me as a rudimentary form of joking—a setup followed by a playful ‘punchline.’

Young children are especially amused by repetitive jokes that involve an element of surprise. Think of games like peekaboo!

This concept of anticipating surprise forms the foundation of much humor. Traditional joke setups like “knock knock,” “what’s the deal with,” and others prime listeners for a punchline, signaling that the upcoming language should be interpreted in a playful, non-literal manner.

Children start engaging in these kinds of humorous interactions before they can even speak. Vasu Reddy, a psychologist at the University of Portsmouth, refers to these as “clowning” behaviors, which include offering and withdrawing objects, disrupting others’ activities, and performing unexpected actions. These actions are not about breaking rules but about engaging with others, often accompanied by laughter and seeking adult attention.

The playful exchanges I witnessed between the infant orangutan and her mother were initially tangential to my main research focus. However, they left a lasting impression and led me to explore the cognitive processes underpinning such communication. This shift in focus brought me to consider teasing not just as an element of communication but as a window into understanding social intelligence.

Orangutans, along with humans, chimpanzees, bonobos, and gorillas, share many traits due to our shared evolutionary lineage. We have large brains, extended childhoods, and complex emotions like joy, sorrow, jealousy, and resentment. We recognize ourselves in mirrors and understand that others may have knowledge we lack. Our social intelligence is advanced; we are deeply interested in others, engaging in various interactions from play and learning to conflict and reconciliation. This intense curiosity about the intentions, emotions, and relationships of others may explain the evolutionary roots of playful teasing.

To explore this theory, we began systematically observing great apes for teasing behaviors, a study that had not been undertaken before. In early 2020, I gathered a team of students, postdocs, and colleagues to initiate hands-on studies at zoos, but the onset of the COVID-19 pandemic forced us to pivot to a video-based approach. We analyzed footage of orangutans, gorillas, chimpanzees, and bonobos from various zoos across the U.S. and Europe, focusing on interactions that blended playful and annoying elements while steering clear of purely aggressive or playful exchanges.

Studying social cognition in animals as complex as great apes is challenging. In human research, we can use questionnaires to inquire about people’s thoughts on others’ intentions or beliefs. However, studying nonhuman apes and human infants requires observing natural interactions or responses to sounds, images, or puzzles, as they cannot communicate their thoughts verbally.

We developed a behavioral coding system for teasing, building upon methods used in ape communication studies. This system involves identifying specific behaviors, their frequency, the identity of the participants, and the nature of the interactions—whether they are one-sided or reciprocal. By applying these codes systematically, we can turn complex real-world interactions into quantifiable data for analysis, ensuring our observations are not merely subjective interpretations.

Our refined coding system highlighted several key features of playful teasing: provocative behavior that’s hard for the target to ignore, surprise tactics like approaching from behind, focused attention on the target’s reaction, and repetitive or escalating provocation. While not all interactions exhibited all these traits, many showed at least three of the five, providing a robust framework for identifying teasing across different contexts and individuals.

Playful teasing offers a safe space to hone social prediction skills, vital for navigating complex social landscapes.

Defining what constitutes provocative behavior was challenging but essential. It needed to be something unequivocal and attention-grabbing, whether through sudden or exaggerated actions. This could range from banging on an object the target was using to leaning in close to their face, actions designed to compel a response.

The great apes we studied—orangutans, gorillas, chimpanzees, and bonobos—exhibit significant differences in their social structures and natural habitats. Orangutans are mostly solitary and arboreal, while gorillas live in ground-dwelling groups led by a single male. Chimpanzees and bonobos are both arboreal and terrestrial, living in large, mixed-gender groups. Chimpanzees show male-dominated, aggressive social dynamics, whereas bonobos are mostly female-led and handle conflicts with sexual behaviors rather than aggression.

Despite these differences, all four species engaged in similar forms of playful teasing. They poked, prodded, tugged, and tickled each other, often incorporating swings, arm waving, and object manipulation into their interactions. Teasers would sometimes interrupt others’ activities by grabbing limbs or using objects to block actions, like a young chimpanzee repeatedly smacking his mother to get her attention while she was engaged in grooming another chimpanzee.

Teasing among apes appeared to be a deliberate attempt to elicit a reaction, expecting an interactive response rather than treating the target as a mere obstacle. This involved watching the target’s reactions closely and adjusting the teasing behavior accordingly, escalating from a simple poke to more annoying actions like pulling hair or hitting.

This type of interaction, while potentially irritating, rarely led to aggressive responses. Targets often ignored the teaser or responded with mild, non-confrontational movements. Sometimes, they engaged playfully or reciprocated the teasing, indicating a mutual understanding of the low-stakes nature of the interaction. This kind of teasing typically occurs during periods of low stress and may be more frequent when apes are bored, such as during long periods of inactivity.

The widespread presence of playful teasing in our closest evolutionary relatives suggests it plays a significant role in their social lives. In humans, teasing serves as a valuable tool for understanding others’ thoughts and emotions. Teasers must anticipate how their actions will be perceived and adjust their behavior based on expected reactions. What might be a funny joke among close friends could be inappropriate or offensive in a different context. This ability to gauge social responses is crucial for species that rely heavily on complex social interactions.

Understanding the intentions and emotions of others is foundational to human language and culture. While nonhuman apes do not use language in the way humans do, they share many underlying cognitive abilities that are illuminated through behaviors like playful teasing. This type of interaction may represent a transition from physical play to mental play, engaging not just with physical actions but with psychological states.

Our research into teasing is just beginning to reveal its role in social cognition in apes and potentially other animals. We’re employing methods like eye tracking to see what captures apes’ attention during interactions, and thermal imaging to detect physiological signs of excitement, such as increased blood flow, which may indicate amusement or anticipation. Although still in early stages, our findings suggest that apes, like humans, experience heightened engagement during playful interactions, hinting at a shared evolutionary basis for these behaviors.

While our study has focused on primates, we suspect that playful teasing might also be found in other highly social animals with complex brains and extended juvenescence, such as dolphins, elephants, and dogs. We’re expanding our research to include these species and encourage others to share observations and insights. By understanding teasing across a broad spectrum of species, we can better grasp its evolutionary origins and its role in the social lives of animals, providing deeper insight into the nature of humor and interaction in the natural world.

Observations of playful teasing in apes suggest that the roots of human humor may be more ancient than previously thought, potentially dating back over 13 million years to our last common ancestor. While they may not be ready for a comedy special on Netflix, these teasing apes offer compelling evidence that humor has a long and shared history across our evolutionary lineage.